การสลายตัวของสารตกค้างยาฆ่าแมลงในพริกแห้งโดยวิธีการรมแก๊สโอโซน

Abstract

Due to the excessive uses of pesticide in the current agricultural farming, the products are normally contaminated with pesticide residue. Gaseous ozone fumigation is the technique that could reduce pesticide efficiently. The objective of this work was to study the effects of ozone fumigation on pesticides residue degradation in dried chili and to study the potential of scale up on ozone application. The first part was conducted by studying the degradation of 6 pesticides, namely, diazinon, malathion, chlorpyrifos, prefenofos, ethion and triazophos. The study also determined the degradation kinetics of pesticide residues, degradation half-life period (t1/2), and dried chili qualities. This includes, total phenolic compounds, antioxidant properties, water activity, color, capsaicin content and physical property of chili surface after gaseous ozone fumigation treatment. Results showed that, after 8 weeks of storage, the of pesticides were naturally degraded in the range of 28-46% with the t1/2 in the range of 66.6-120.9 days. After dried chili was fumigated with gaseous ozone for 30 min in a pressurized tank, pesticide residue exhibited the degradation in the range of 45-69% with the t1/2 in the range of 17.4-32.1 min. Compared to the natural degradation, the ozone fumigation is better and more effective to degrade the pesticide by 99.9%. Furthermore, ozone fumigation didn’t significantly affect (p ≥0.05) chili surface morphology, total phenolic compounds, antioxidant properties, water activity, color and capsaicin content of dried chili. In second part, the vertical force air circulation (VFA) was applied to the ozone fumigation process and the study of dimensionless parameters to determine the potential of system scale up was conducted. The Buckingham PI - theorem was applied to obtain dimensionless parameters of the VFA fumigation analysis. It was found that, the Reynolds number (Re) corelated with hydraulic diameter and pressure drop. The reduction of chlorpyrifos residue under gaseous ozone fumigation using VFA technique was in a range of 49-77% throughout the vertical stacking column of chili. Moreover, ozone fumigation with VFA was able to improved the ozone fumigation on degradation efficiency by 28% and save operation cost by of 34% compared to conventional ozone fumigation. The relationship between pesticide residue degradation and dimensionless parameters could be used for commercial scale-up in terms of stacking height, air flow rate throughout chili basket, and pressure drop. The findings from this study provide benefit of the gaseous ozone fumigation to reduce the pesticide degradation in dried chili with VFA system that can be scale-up for the commercial application.